1. Field of the Invention
This invention relates to toilet systems that treat flushed human waste from a toilet or urinal and more especially relates to toilet systems that macerate the flushed human waste followed by an evaporation of part of the water content to reduce the volume of waste that is stored until it can be discharged.
2. Description of the Prior Art
Broadly speaking there are two general types, recirculating and nonrecirculating, of toilet systems that receive human body waste.
The recirculating toilet systems are particularly useful on airplanes. For these systems it is necessary to provide initially in a waste-receiving tank a limited amount of flush water. The flushed waste flows into that tank. During each subsequent use filtered water is pumped to the toilet as flush water from the accumulated mixture of initial water and increasing content of human body waste. These recirculating toilet systems minimize the amount of flush water required to be added to the airplane at the start of a period of service of the toilet system in the airplane. Some systems of this type provide a periodic withdrawal from the tank of a part of the accumulated mixture of body waste and initial flushing water to another tank in which it is heated to evaporate part of the water content. The latter systems of this type are disclosed in assignee's U.S. Pat. Nos. 3,535,712 and 3,536,196. In these patents it is disclosed that this evaporation of part of the water content produces a slurry that can be incinerated. In both of these patents the evaporated water content is vented to the atmosphere and it is disclosed that the vapor from the evaporation tank can be passed through a biological filter before venting the water vapor to the atmosphere. The incineration of the slurry to ash after the evaporation can be performed in the same tank when the heated tank etc. are suitably constructed.
In another recirculating toilet system, that is shown in U.S. Pat. No. 3,831,534, the accumulated mixture of initial flush water and human body waste is periodically transferred to an incinerator in which the liquid content is evaporated and discharged and the solids are converted to ash by a combustion flame.
A modified recirculating toilet system is disclosed in U.S. Pat. No. 3,733,617. In that system the human waste is macerated during transfer to a tank from which it is fed to a heated vacuum chamber in which volatile liquid of the waste is evaporated while the solids are withdrawn from the bottom as dehydrated waste. The evaporated liquid is condensed and that liquid is transferred to a vessel from which it is pumped to the toilet for the flushing of the toilet.
U.S. Pat. No. 3,700,565 discloses a toilet system in which the flushed human waste is transferred from a receiving tank to an evaporating tank in which the liquid portion of the waste is vaporized by microwave energy. The evaporated water content is vented to the atmosphere.
The nonrecirculating toilet systems are used in facilities including mobile vehicles, such as passenger railroad cars and marine units, that have available a source of flush water that is not limited as is the case for the recirculating toilet systems installed in airplanes. These toilet systems when installed, for example, in passenger railroad cars and marine units, do not have the capability of transferring the flushed human waste to a sanitary sewer system as is the case for those nonrecirculating toilet systems installed in homes. In the past the toilet systems in passenger railroad cars merely dumped the flushed waste along the railroad right-of-way during the travel of the train. In the case of marine units the human waste from toilet systems was dumped overboard without any treatment.
Various systems have been developed to treat the human waste before dumping it. One system, that is illustrated by U.S. Pat. No. 3,846,847, includes means to add a tablet to the flushed waste prior to its maceration. The macerated waste is transferred to a decontamination tank. The tablet provides a chemical decomposition of the waste. The product is dumped. In the marine toilet system of U.S. Pat. No. 3,699,592 flushed human waste is macerated and chemically treated before dumping overboard.
Other patents that disclose toilet systems in which the flushed waste is chemically treated include U.S. Pat. Nos. 3,557,388, 3,563,384 and 3,713,177. U.S. Pat. No. 3,568,215 discloses a toilet system in which the sewage is treated electrolytically and then the treated sewage is reduced in volume by evaporation.
The addition of a chemical tablet or fluid to the flushed waste requires equipment to dispense the chemical during the transfer operation and it is necessary to ensure that the supply has not been depleted. Chlorination has been used to destroy bacteria prior to discharging the macerated flushed waste from the toilet system. The chlorination is not totally effective for the treatment of human waste containing solids and it does not necessarily kill the spores and viruses. Of course, it is desirable to avoid handling of chlorine tanks for their connection into a toilet system for treating flushed human waste.
Instead of a chemical treatment of the entire flushed waste the toilet system described in U.S. Pat. No. 3,548,421 provides a separation of the flushed waste to provide a solid waste matter that is incinerated and a liquid that is subjected to a chemical treatment. In toilet system of U.S. Pat. No. 2,768,386 the flushed waste is homogenized and then transferred to an incinerator in which the liquid content is volatized and discharged to the atmosphere and the solids are incinerated in the same operation.
Assignee's U.S. Pat. No. 3,787,901 claims a toilet system in which the flushed human waste is macerated and then transferred to a storage tank in which the macerated waste is heated to evaporate water for a volume reduction of the waste. In the system of this patent the water vapor is disclosed as merely vented to the atmosphere from the evaporator tank. In the event that it is desired to treat the resultant concentrated flushed waste at the site of the toilet system, the toilet system further includes an incinerator to which the concentrated flushed waste is transferred for its conversion to gas and solids.
As seen below, the toilet system of the present invention includes a catalytic oxidation treatment of the vapor evolved from heated flushed waste in an evaporator tank. U.S. Pat. No. 3,487,016 discloses a method of purifying waste water by catalytic oxidation. Organic and inorganic materials in the liquid or vapor phase are catalytically oxidized using oxygen-containing gas and a catalyst such as acid treated MnO.sub.2. That patent mentions a number of earlier U.S. patents that describe processes for catalytic oxidation of waste water.
U.S. Pat. No. 3,127,243 describes a process of recovering potable water from flushed human waste. In the apparatus using the process the entire system is at a low pressure, e.g., 60mm.Hg. The waste is heated to volatilize water and some of the other ingredients of the waste. This vapor is mixed with a very small amount of air and the mixture is passed through a high temperature catalytic zone containing platinum and then cooled to condense water. The test data indicate that a catalytic treatment at a temperature of about 500.degree. C. is required to provide condensed potable water.
A jacketed tank has been used to heat, by steam in the jacket chamber, various foods containing water to provide canned soups etc. One tank construction that is commercially available is used as the preferred evaporator tank in the present invention. That commercial tank includes some, but not all, of the electrical components used in the preferred embodiment of the present invention to control the operation of the heater for the tank. The differences are described below after the detailed description.